1. Field of the Invention
The present invention relates to a stop device for use in optical equipment.
2. Description of the Related Art
Conventionally, a lens barrel using a flare stop is known as proposed in Japanese Unexamined Patent Publication No. 5-188274. The sectional views of FIGS. 8A, 8B and 8C show the operating state of the flare stop. The flare stop device of the lens barrel comprises a third lens barrel 60, which is advanced and retracted to and from a fixed frame 101 by a zooming operation and a collapsing operation, a float key 80, whose distance in an optical-axis direction changes with respect to the fixed frame 101 and the third lens barrel 60 in the zooming operation and the collapsing operation, a flare stop 100, which is locked to the float key 80 and interposed between the fixed frame 101 and the third lens barrel 60, and so forth.
The flare stop 100 is a thin disc having a flare stop opening 100c formed at the center thereof. The flare stop 100 includes an annular peripheral wall section 100b formed at the outer peripheral portion thereof in a forward direction, an elastic piece 100a extending in the forward direction from the trisected position of the front surface of the annular peripheral wall section 100b, and a locking pawl 100d formed at the outer peripheral portion of the extreme end of the mounting piece 100a. 
The flare stop 100 is mounted in such a manner that it is engaged with the float key 80 along the inner peripheral wall 80f of the float key 80 from the rear side thereof so as not to interfere with the third lens barrel 60, and the locking pawl 100d of the mounting piece 100a is elastically inserted into the rectangular engaging hole 80e of the float key 80. As a result, the flare stop 100 can move in the optical-axis direction by the length of the engaging hole 80e rearward of the float key 80.
The operation of the flare stop 100 in zooming and collapsing will be described with reference to FIGS. 8A, 8B and 8C. First, when respective lens groups are retracted, the flare stop 100 is in a state shown in FIG. 8A. In the collapsed state, the flare stop 100 is abutted against the mask front side 101a of a main body 101. The locking pawl 100d of the flare stop 100 is located at a position near to the front end of the engaging hole 80e of the float key 80.
Next, when the respective lens groups are driven to a wide-angle state, the flare stop 100 is in a state shown in FIG. 8B. In this state, the third lens barrel 60 relatively moves backward by a distance F2 in the optical-axis direction with respect to the float key 80 while the float key 80 moves in the optical-axis direction. With this movement, the rear end surface 61a of a lens support frame 61 which is engaged with the third lens barrel 60 is abutted against the front end surface 100f of the flare stop 100, thereby pushing out the flare stop 100 toward the rear side of the optical-axis.
Next, when the respective lens groups are zoomed up to a telephoto state, the flare stop 100 is in a state shown in FIG. 8C. In this state, the third lens barrel 60 moves by a predetermined distance in the optical-axis direction. However, the relative positional relationship between the float key 80 and the flare stop 100 is not changed from the wide-angle state because the movement of the third lens barrel 60 does not physically affect the flare stop 100. Then, the flare stop opening 100c is located at a midway position between a third lens group L3 and the mask front side 101a and doe not interfere with an effective light beam OP in the telephoto state.
However, in the flare stop device of the lens barrel in Japanese Unexamined Patent Publication No. 5-188274 mentioned above, the flare stop 100 is held to the float key 80 by the elastic force of the mounting piece 100a. Thus, the locking pawl 100d of the flare stop 100 can be moved at least within the range of the engaging hole 80e of the float key 80 between, for example, the wide-angle state in FIG. 8B and the telephoto state in FIG. 8C. The flare stop 100 itself has little possibility that it moves because it is composed of a light member. However, when strong shock is applied to the main body, there is a possibility that the locking pawl 100d will be released from the confines of the engaging hole 80e, i.e., from the range in which it normally moves.
An object of the present invention, which was made to overcome the above disadvantage, is to provide a stop device which can accurately maintain the relative distance between the stop member and the frame member for supporting it and which further occupies a small space and is effective to reduce the size of the lens barrel to which the stop device is assembled.
A stop device of the present invention comprises a stop member having arm sections including convex portions at the extreme ends thereof and permitting a desired photographing light beam to pass therethrough; and a frame member having a first sliding surface on which the convex portions can slide, a second sliding surface, on which the convex portions can slide, having a step with respect to the first sliding surface and an inclined surface for continuously connecting the sliding surfaces and capable of moving in the optical-axis direction of the lens barrel about the optical-axis thereof, wherein the stop member slides on the first sliding surface when the lens barrel moves from a collapsed position to a photographing preparation position, slides and falls on the inclined surface and reaches the second sliding surface when the lens barrel moves from the photographing preparation position to a first photographing magnification position, and slides on the second sliding surface when the lens barrel moves from the first photographing magnification position to a second photographing magnification position.
Other features and advantages of the present invention will be apparent form the following description when taken in conjunction with the accompanying drawings.